AN exceptionally dry spring has significantly reduced soil moisture levels and growers may have to intervene to mitigate potential crop stress during the crucial canopy-building stage, according to agronomy firm, Hutchinsons.

“While we are some way from drought conditions, the level of moisture is surprisingly low under many winter cereal and rape crops and the current forecast predicts only average rainfall at best for May,” said its technical manager, Dick Neale.

“When soils begin to rapidly dry, it is important to react in the earliest stages of moisture stress, rather than take action three to four weeks after the impact has set in.”

Plant responses to drought stress are complex, but there are two key areas that growers can focus on. These are to support photosynthesis and build root structure to improve scavenging ability for water and nutrients, he argued.

Magnesium plays a central role in photosynthesis, but is one of the first nutrients to decline in availability during dry conditions, so it is important to maintain levels according to crop need. Also potassium availability drops markedly in dry soils, so a foliar application may be beneficial given the nutrient’s role in cell turgor, he added.

Like potassium, nitrogen is required in larger amounts to build canopy and is vital for most energy-driven functions within plants, so he recommended applying a foliar product, such as N-Durance 28, or Persist-N, which will be more available than granular applications reliant on soil moisture for uptake. Additional sulphur may also be needed to support nitrogen utilisation.

Growers applying standard liquid nitrogen should take care to avoid scorch, though, as this can be highly damaging to moisture-stressed crops, he said.

Mr Neale also pointed out that research increasingly showed a benefit from applying boron between GS 39 and GS 45, even under severe moisture stress. This element is important in germ tube formation, pollen and flower fertility.

A final option is to consider applying an amino acid-based biostimulant, which can help alleviate the impact of stress on crops by reducing the accumulation of damaging metabolites within plants and by stimulating rooting. Seaweed extract-based products can also relieve stress responses, he pointed out.